//#pragma GCC target ("avx2,sse2")
//#pragma GCC optimization ("Ofast")
//#pragma GCC optimization ("unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree <pair <ll, int>, null_type, less <pair <ll, int> >, rb_tree_tag, tree_order_statistics_node_update>
#define ll long long
#define ull unsigned long long
#define db double
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define fi first
#define se second
#define mp make_pair
#define up_b upper_bound
#define low_b lower_bound
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define endl "\n"
#define left fsdsdfoisf
#define sum dpsdfioppsf
#define assign xcvjlkdjfio
#define trie fksdfkjkfnjuiv
#define next sidlfjsfkl
#define merge sdfksdkfsldf
#define int long long
using namespace std;
void dout() {
cerr << endl;
}
template <typename Head, typename... Tail>
void dout(Head H, Tail... T) {
cerr << H << ' ';
dout(T...);
}
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef pair <int, int> pii;
const int N = 2007, inf = 1e18;
int n, dp[N][N];
vector <pii> v;
void solve(int tc) {
// check for (int i = 0; i < n; j++)
cin >> n;
n *= 2;
for (int i = 0; i < n; i++) {
int x, y;
cin >> x >> y;
v.pb({x, y});
}
sort(all(v));
for (int i = 1; i <= n; i++) {
for (int j = 0; j <= i; j++) {
dp[i][j] = inf;
if (j < i) {
dp[i][j] = min(dp[i][j], dp[i - 1][j] + abs(2 - v[i - 1].se) + abs(i - j - v[i - 1].fi));
}
if (j > 0) {
dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + abs(1 - v[i - 1].se) + abs(j - v[i - 1].fi));
}
}
}
cout << dp[n][n / 2];
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
int tc = 1;
// cin >> tc;
for (int i = 0; i < tc; i++) {
solve(i);
// cleanup();
}
}
